PD-1 expression and its correlation with tumour infiltrating lymphocytes and Ki67 in patients with breast cancer

Introduction: Immunotherapy targeting the programmed death-1 (PD-1) checkpoint has resulted in good outcomes in patients with melanoma, non-small cell lung cancer and head and neck cancer. Recent data have showed that patients with ER/PR negative breast cancer might benefit from immunotherapy as well. We investigated PD-1 expression on tumour infiltrating lymphocytes (TILs), the presence of TILs and Ki67. Furthermore, the association of PD-1, TILs and Ki67 with time to metastasis was statistically determined. Methods: Resection specimens of 284 patients with an ER/PR negative invasive ductal adenocarcinoma of at least 2 cm were analysed. Haematoxylin-eosin staining was performed to determine the percentage of TILs. Subsequently these percentages were divided into three groups: less than 10%, 10%-30% and more than 30% which matches with respectively 30%, 50% and 20% of the patients. PD-1 expression on the TILs of 116 patients and Ki67 expression of 185 patients were assessed using immunohistochemistry. Results: An increase in the fraction of TILs was significantly associated with a lower risk of metastasis (hazard ratio [HR] = 0.7, 95% CI = 0.6-0.9). PD-1 expression on TILs was observed in 97% of the patients. Three patients had no expression of PD-1, this lack of PD-1 expression significantly increased the risk of metastasis (HR = 5.541, 95% CI = 1.2-25.0). No association could be noted between PD-1 expression and the amount of TILs or Ki67 (p-values of respectively 0.272 and 0.637). Similarly, no association could be noted between Ki67 and the amount of TILs (p-value = 0.1954) Conclusion: PD-1 was expressed on TILs in patients with breast cancer. Surprisingly, no correlation was found between PD-1 expression and TILs or Ki67. However, an increased amount of TILs was significantly associated with a lower risk of metastasis.status: publishe